I first found out that the lift I made for the bkie doesn't get the front wheel off the ground (only the rear wheel):

And under the bike:

So I came up with a way to get the front wheel up so I could spin it if needed. Toolbox and a few scrap pieces of wood did the trick:

Removed the caliper mounting bold and slid the caliper up and off the disc. Covered the wheel with some old t-shirts so the brake fluid wouldn't get on the wheel.

Loosened the union bolt and allowed the brake fluid to drain into a bottle. Was careful not to lose the sealing washer on the end of the bolt (mine dropped into the bottle and I had to fish it out. A bit of brake fluid will drip onto the caliper, but as long as you continue loosening the union bolt quickly, you can get most of the fluid into the bottle.

I wrapped the end of the brake line in a t-shirt and stuck it back up in the fork to get it out of the way. The caliper assembly has a pin that slides into the caliper pin boot on the mounting plate that remains connected to the fork and you remove the caliper by simply pulling it away from the disk.

I now had my caliper completely off the bike. The two pins that hold the brake pads in the assembly slide out (I pushed them out with an allen wrench). I took the pads out and sprayed them down with brake cleaner. Having no idea what a set of new pads looks like or what a set of worn pads looks like, I took a picture and would like some feedback. Should I replace the pads? The bike has 24,000 miles on it and as I am the 3rd owner I have no idea if they have ever been replaced.

In the link to the other thread above, there is mention of pad mounting clips. I don't know if the dual piston caliper on the 450 has these, but I didn't run across anything that seems to fit the description of these. So does anyone know if the 450 has them? Am I dealing with a situation where my brake should have them and they were discarded?

I haven't gotten into the actual process of "rebuilding the caliper" as outlined in the Clymer manual, but here is a picture of my caliper. Any thoughts on how it looks?

Am now debating whether or not I need to clean and rebuild the caliper with new seals etc. Without putting it all back together, I don't know if the constant contact will be fixed by cleaning (or replacing) the pads and using some brake quiet when I reassemble or if the problem is because the pistons were stuck...thoughts?

For what it's worth, on that type of lift, if I know I will need the front wheel to spin, I usually lay out a tie-down strap (the type used to secure a bike for transport) so that the lift itself pins one end to the ground. I then loop the other end through the rim of the back tire and pull (or ratchet, depending on the straps) the cinch. This tugs the rear end down easily, and lets the front wheel come up.

Now for your pads:

a couple of profile pics would have been a big help, but from what I see in these pics, you should have replaced them quite some time ago. If I am seeing this correctly, the 'buttons' are exposed. These are the points at which the pads are either bonded or riveted (vaires from brand to brand) to the back plate. Generally, a pad is worn out before these are so clearly visible. Once the buttons are exposed, the remaining material is thin enough that it no longer dissipates heat properly and can simply crumble away at any time.

And from the looks of surface of the pads (again, I can't really make out the details needed for confirmation), it's a fair bet your rotors are gouged as well. How did they look? Gouged rotors will wear out new pads faster, as they do not make full contact across the whole surface of the new pad. Also, they do not dissipate heat as well, and are more prone to warp. All of this will reduce your braking capacity.

Going from these pictures, definately change the pads.

And the calipers:

I don't know if your 450 needs pad clips or not, but if you don't have them, don't worry about it too much. You can substitute disck brake pad adhesive to reasonably do the same job. (I like the permatex brand stuff myself, followed by the Copper Cote brand). Simply spray one or two thin coats (don't put it on too fat; it's not paint, and using too much will negate the benefits) onto the backs of the pads. Let it set up for a few minutes until it is good and tacky. Install the pads and pump up the brakes. Once you have regained a good firm brake lever, the pads are lightly stuck to the caliper and the piston, which is really all the clips are intended to do. And frankly, on a bike twenty years old, odds are those clips weren't much up to the job anyway (If you ever had any, that is).

As far as rebuilding the caliper, that is more a decision you will have to make on your own. For what it is worth, it is inexpensive and easy to do, and is the best way to completely flush any old brake fluid from your caliper.

When you were braking, did the brakes ever seem to bind or fade or perhaps cycle between the two? Did they apply smoothly, only to get grabby suddenly? When taking off from a stop, did you ever feel that you were briefly fighting against the brakes, as if they had not completly released yet? Was there any evidence of leaking? When you inspected the caliper and pistons, was there any evidence of pitting on the pistons themselves?

There are questions that can lead directly to a caliper rebuild. Most commonly, pitted pistons or calipers that fail to release on demand.

But again, it is easy to do, and hard to screw up. If you just want to do it, there is no reason that you shouldn't.

Was the caliper actually sticking? I know you said that the pads were in constant contact, but the thing here is that without spring clips or brake quite type adhesives, they generally will be; there is nothing to pull them back off the rotor, even after the piston pressure has been released. And even with one or both of these methods, the fact is that the caliper piston does not ever 'suck back' into the caliper; it simply stops applying active pressure. If a rotor is gouged very deeply (not that common on a solid disk), it is possible that the pad is actually clinging to the disk like a little slot car.

Thanks guys...since I didn't really know what pads are supposed to look like, it appears that I wore out my welcome on one of them. The one on the left with the buttons exposed has a profile like this and appears to have no "pad" left:

The one on the right has some left, and again I don't know what they look like new, so I don't know how worn this one is:

So new pads it is.

As far as the rotor being gouged, here are a couple of shots where I did my best to show the surface:

I can feel the ridges in the rotor, but don't know how bad they are and am not sure if you will be able to tell anything from these photos. If you can, give me your thoughts. I understand that with even some gouges, this rotor will wear my new pads more quickly. Looks like I might need to go invest in some type of micrometer to be able to measure the thickness to see if it has enough left to be reworked?

On the caliper rebuilding front, Duke, to answer your questions:

The brakes did fade or bind regardless of pressure applied, speed when applied or any other variable. I never felt as though I was fighting the brakes when accelerating from a stop either. No evidence of leaking at all. As you can see from the picture, the pistons aren't clean, but I don't really see any pitting or gouges in them. With the lack of all of these symptoms, this is why I didn't necessarily think I had worn the pads down so far (until I tore into the caliper and got your feedback on them).

Was the caliper sticking? When I got the front wheel up off the ground and spun it, there was definite contstant contact. However, I was able to move both pads easily as you described in the other thread where you went through some of the things to check and do for squeaking brakes.

I will say that when I went back out to take the pictures of the disk and pad profiles, I attempted to push the pistons back into their cylinders. When I did this, some additional brake fluid came out of the caliper, of course, but I wasn't able to push one of the pistons in very much at all. This picture shows how far I was able to get one of the pistons (and I think I could have pressed it in a bit further if I wanted to), but the other piston won't budge much.

This (and your reassurance that it is an easy task) leads me to believe that a rebuild is next on the list.

Pads, pistons, seals, core (the caliper "body") is the complete list of parts. There is nothing else. Like I said: super simple job to do.

Pressing the pistons back into the caliper is necessarily difficult, particularly when the hydraulic system is closed. Don't think that a hard push is sufficient reason to rebuild. As you remembered, if you can easily wiggle the pads when the brake is not applied, then the caliper is most likely not binding. But again, there is no real good reason to _not_ rebuild it, if it will give you more piece of mind.

Keep in mind that if you are going this far into the process-- rebuilt caliper, drained fluid, etc, you might want to consider a complete flush of the master cylinder as well. Brake fluid is--- what's that word? Hydro-something or other.... At any rate, it ruins with age, and it will absorb scads of moisture when the system is opened. Go ahead and do a complete flush.

Good to know about the pistons being difficult...I was just concerned that I was able to push one in quite a bit (with some work), but the other wouldn't budge. The system is open now that the brake line is disconnected...would have thought both pistons could be moved.

I was planning a complete flush of the system while I was at it...I believe the term is hydrophillic (water loving).

Looks like you guys have everything under control! I'll only add one piece of advice for the disc brake system...

Typically the pads will have a notch in them that you can see while the brakes are together on the bike. This notch is the wear indicator for when you should replace the pads.

In the automotive world, I believe the pads are suggested to be replaced when they are half the thickness of the backing plate, but every bike I've ever seen has had this notch or groove in the pad material itself.

I was thinking that perhaps the groove doesn't start showing until the pad is worn down to a certain point. Thus, the fact that my pad is showing all 3 grooves, it might be all the way to the wear indicators and needs replaced?

I'm replacing both regardless and perhaps will learn a bit more when I get a set of new pads in my hands to see what they look like...

Took the caliper over to a friend that has an air compressor so I could pop the pistons out per the Clymer manual. Will say that we needed every bit of the 80 psi to blow the pistons out and what Clymer says about not putting the air directly into the hole, but rather hold at an angle so some air can shoot off to the side of the hole...DIDN'T WORK. Figure that Clymer is just trying to play it safe so no one gets hurt with the pistons flying out due to too much air, but we had to almost create a complete seal between the nozzle and the hole to blow them out. We did keep a t-shirt wrapped around the caliper so they wouldn't go flying...

Here is a pic of the caliper withouth the pistons and also without the brake pad spring:

Used a wooden toothpick to remove the dust seal and the piston seal in each cylinder and they looked like this prior to cleaning:

Most of the dirt and grime was on the end that was exposed out of the cylinder (makes sense) and the end that stays in the cylinder was pretty clean. Used rubbing alcohol to clean them off per Clymer and they turned out like this:

Ordered a caliper rebuild kit from Jack today for about $18 or so...essentially is the dust seals, piston seals and boots (all the rubber parts in the caliper) for the caliper. Also ordered a new set of pads for $28. I am also going to replace the brake pad spring, but Jack didn't have that, so I'll order from BikeBandit. Jack was cheaper on everything else (as usual!).

Next step is to clean out the caliper prior to rebuilding...

When Duke talked about doing this in the other post I referenced at the very beginning of this thread, he said to use tranny fluid for it's detergent properties, then solvent, then acetone prior to coating with clean brake fluid. What do you use as your solvent? Since I don't have tranny fluid, solvent (I don't think) and acetone handy, is there an acceptable alternative? Clymers suggests rubbing alcohol again...good enough?

Typically the pads will have a notch in them that you can see while the brakes are together on the bike. This notch is the wear indicator for when you should replace the pads.

There is a separation down the center of most pads--sometimes more than one, like the second pad in Smunderdog's picture, from 'top' to 'bottom' when you are holding the pad so that it is widest from left to right. This notch is actually to assist with cooling the pad, but it does serve as a handy reference to show you how much "meat" is left on your pad. But make sure that you look at each pad. Just like Smudy's, with the style of caliper these bikes use, odds are the pads aren't going to wear evenly. Smundy, your pads should have been changed a _long_ time ago.

Smunderdog wrote:

Good to know about the pistons being difficult...I was just concerned that I was able to push one in quite a bit (with some work), but the other wouldn't budge. The system is open now that the brake line is disconnected...would have thought both pistons could be moved.

Actually, with the brake system open, you should be able to force them back in by hand. It _should_ be fairly easy, but as you have seen, it isn't always. Sometimes a build up behind the pistons or the seals -- sediments and such (especially common in cast iron calipers)-- can hamper the movement of the piston. Also, with age, pistons can develope a bit of wear, a kind of groove around their circumference, that they don't like to leave. Lay your piston on a perfectly flat surface to see if it is worn in this way, or use a straight edge and extremely steady hands.

Another problem that can hamper piston movement is surface rust on the piston (grabs the seals on the way by) and pitting. If it is pitted, replace it. Sure, you can run it some more, but it'll just eat your new seals up faster, and you'll end up doing this again a lot sooner than you would like, or learning to love the smell of brake fluid as it leaks onto your hot rotor....

And the final-- and generally most common-- reason that your piston might be hard to push in or dislodge is simple physics. It isn't as easy as it seems to be to push those rascals perfectly straight, and that's the only way that you are going to get them to budge.

As for the air pressure,

the Clymer's manual is actually right with that part: you should not have to plug the hole around the blow gun to get the calipers to come out. They should pop out easily.

It's not that they are 'covering their bases' there (though I can see why that would be a good idea!); air pressure inside an unloaded caliper can blow the pistons out with enough force to shatter them (they are hardened) or even knock a chunk out of the caliper. That's the biggest reason I mentioned --- way back. Maybe this thread; maybe an older one-- putting the pads in the caliper as a buffer of sorts in case the pistons did come cannon blasting out.

Honestly, if it took that much pressure to get the pistons out, you were due for a rebuild anyway. Good choice.

And as always, good luck.

And I don't know about a sticky; I think I'll just put a link to this thread in the FAQ under brakes.

Acetone is my personal favorite for after the cleaning is done, simply because it gets all the moisture out, and does so in a hurry.

But alcohol is a decent second. Get some in your system, and then set about cleaning ! Seriously-- use a good strong degreaser, if that's what you have, then carefully rinse all of it out per the instructions on the package (and do keep in mind that pentrating oils, while possesing solvent properties, are _not_ good for this application!) then clean out every little bit of residue and moisture with the alcohol.

Oh and when using all those nasty chemicals, I have lately taken to wearing vinyl disposable gloves to keep them off my hands. Walmart has them. Actually, I like wearing them for most routine mechanical work, since they don't interfere with "feel", and your hands stay clean and the carcinogens in the old oil and such don't get absorbed into your skin. To clean up you just peel them off.

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